For this application, TI recommends the following steps:
- Decide how the device shall receive the register settings to plan for in-system programming of the EEPROM.
- Choose which operation mode to use on the device
(I2C or GPIOs) and which pins are inputs and which are
outputs (see registers
GENERIC0
, GENERIC1
, and GENERIC2
). - Consider that the serial interface and the GPIOs are supplied by VDDREF as well as the input pins (for example, a 3.3-V crystal oscillator (XO) driving XIN forces uses 3.3-V I2C).
- Keep track of which voltage levels the output
supplies will have. There are configuration bits in the output channels (see
CH1_CTRL5,
CH2_CTRL5
, CH3_CTRL5, and CH4_CTRL5). - Consider which output frequency has the most stringent phase noise specifications. Select this frequency to decide on the reference and VCO frequency.
- Cross-check if your specific bandwidth
requirement for an external reference can be achieved using the internal
loop filter components (see registers PLL1 and PLL2).
- Optimize the clock distribution using output muxes to run the least amount of blocks to conserve power,
- For HCSL output buffer format, optimize the signal integrity and slew rate at the receiver input using a series resistor between device pin and the 50 Ω termination to GND.Y1,Y4 provide higher slew rates compared to Y2,Y3.
Use Equation 1 through Equation 4 to calculate the a basic frequency plan or use the provided software TICS Pro to generate settings.
Note: The user has to ensure PLL stability is given by applying the adequate loop filter and charge pump settings. A phase margin of ≥ 68° is recommended. The target bandwidth is recommended between 600 kHz .. 1100 kHz.
Equation 1. fY0 = fXIN = fREF
Equation 2. fPFD = fREF / ip_ref_div
where
- ip_ref_div ≥ 1
- 1 MHz <= fPFD <= 100 MHz
Equation 3. fVCO = fPFD · pll_nc · (pll_ps + 4)
with
- 2400 <= fVCO <= 2800
- 0 <= pll_ps <= 2
Equation 4. fY[4:1] = fVCO / ((pll_ps[ab] + 4) · ch[4:1]_iod_div)
with
- 0 <= pll_ps[ab] <= 2
- 1 <= ch[4:1]_iod_div <= 16383
- 44.1 kHz <= fY[4:1] <= 350 MHz
with
- 1 <= IP_REF_DIV <= 255
- IP_EN_DBLR = 0
- 1 MHz <= fPFD <= 100 MHz
with
- IP_REF_DIV = 0
- IP_EN_DBLR = 1
- 1 MHz <= fPFD <= 100 MHz
with
- 2400 <= fVCO <= 2800
- 0 <= PLL_PS_MODE <= 2
with
- 0 <= PLL_PS[AB]_MODE <= 2
- 1 <= CH[4:1]_IOD_DIV <= 16383
- 44.1 kHz <= fY[4:1] <= 350 MHz